Modern bicycles usually have several sprocket wheels, also known as chainrings, attached to or mounted on the pedal crank mechanism. A front derailleur serves to change the drive chain from its engagement with one chainring to engagement with an adjacent chainring. To do so, it has a chain guide which is moved in a direction across the plane of the chainring by means of a parallelogram mechanism and acts directly on the chain.
The essentially good function of a guide for the drive chain due to the chain guide cannot, however, with absolute certainty prevent the drive chain from becoming disengaged and slipping laterally on the inside of the smaller of the chainrings and entering the space between the chainrings and the bicycle frame when switching from engagement on the larger chainring to engagement on the next smaller chainring. For the cyclist, there is no possible way to return the chain back to one of the chainrings, which is a severe disadvantage, in particular, in a racing situation.
For this reason, additional chain guide devices, also known as “chain catchers,” have been introduced; they are installed directly or indirectly on the bicycle frame in addition to the derailleur. One embodiment of such a device is disclosed in U.S. Patent Application No. 2011/0230287. The chain catcher used there is an elongated part with multiple bends, which is clamped securely with the same screw used for fastening the derailleur on the derailleur holding part. One disadvantage of such a device is the need to perform the adjustment of both components simultaneously when the derailleur and the chain catcher are installed. The derailleur must be aligned in height and also in the angular orientation in relation to the seat tube of the bicycle frame and optimized with respect to its ability to effect chain shifting between two or more chainrings. The chain catcher must be positioned in its lateral position in relation to the smallest chainring without disturbing the optimal position of the derailleur, which is possible only with great difficulty.
There is a need therefore, for a chain catcher that is simple to install and adjust. The invention satisfies the need.